The present invention relates to agglomerates and more particularly to the recovery of coke fines in agglomerate form for use in cupola scrap melting.
As is well known, in basic oxygen steel making, hot metal from a blast furnace is discharged into a basic oxygen furnace for further processing and refinement. The blast furnace produces hot metal by reducing iron ore. The construction and operation of such a blast furnace, however, is an elaborate undertaking and requires a large capital investment.
An alternative method for producing hot metal for a basic oxygen furnace is to melt steel scrap in a cupola furnace. In addition, cupola furnaces may also be used to melt scrap for direct use in foundry casting. In order to melt scrap in such a cupola furnace, scrap, large pieces of coke, and other ingredients are charged together into the furnace. Air is then bottom blown through tuyeres to ignite the coke and thus melt the scrap. Other ingredients often added to a cupola furnace include limestone and fluorspar or other slag conditioning agents. These ingredients assist in making a slag which is used to remove impurities such as sulfur which are introduced into the steel through the coke.
Cupola furnaces differ from blast furnaces in their need or requirement for large particle charges. Blast furnaces, for example, are generally charged with ingredients having a particle size diameter between 1/2 and 2 inches. Cupola furnaces, on the other hand, operate under low pressures and require larger sized particles, generally between 2 and 10 inches in diameter.
For example, before coke is charged along with scrap and other ingredients in a cupola furnace, the coke is generally screened over a 2 or 3 inch screen. The coke particles having a size greater than 2 inches are then charged into the furnace, and the remainder of the coke screenings are discarded or resold at a lower price due to their undesirable small size. The minus 2 inch coke screenings which are generally discarded are not utilized in cupola furnaces, as they tend to fill the void spaces therein which are necessary for the free movement of combustion air at low pressures across the charge bed.
It is a principal object of the present invention to agglomerate these normally discarded coke screenings into a useable form for cupola scrap melting operations, or any other process which requires the use of coke agglomerates. The necessary parameters for such an agglomerate are as follows: (1) the agglomerate must combine the undersized coke into a large coherent piece or size to allow for proper gas flow in the furnace; (2) the agglomerate must have sufficient load bearing capabilities to maintain its integrity at elevated temperatures in the furnace; (3) the agglomerate should be sufficiently strong to withstand handling and charging into the furnace; and (4) the agglomerate should introduce a minimum of undesirable elements into the scrap melting operation.
The present inventors have discovered such an agglomerate for use in metallurgical processes as will be described in more detail hereinafter.